Electromagnets are used in many sectors in engineering. They are known, for example, as final control elements for hydraulic valves etc. There are a large number of applications in which it is important to ensure that the armature has attracted, i.e. that the armature has arrived in its end position. This results in a characteristic course in the current/time graph, as is indicated, for example, in FIG. 2 (the magnetic voltage can serve in place of the current).
German Patent Application 197 33 138 in particular is known in this regard in the prior art. As claimed in the solution proposed here the magnetic current is converted into a current-proportional voltage and the converted voltage differentiated. This differentiated magnetic voltage is compared with a threshold value. This threshold value is averaged from the differentiated magnetic voltage.
The drawback of the method known in the prior art is the relatively high number of subassemblies. The magnetic voltage must initially be differentiated, a reference voltage only then being obtained by averaging from the differentiated magnetic voltage. In addition to the increased failure probability owing to the greater number of components, there is also the risk in this method of a falsification of the result as the measured voltage is multiply changed by the subassemblies.